This invention relates to a method and therapeutic adhesive patch product for treating trauma blisters, burns or exposure to chemicals.
Blisters of the skin can be caused by repeated trauma due to chafing against the skin, most commonly experienced on the hands and feet or from other causes. Further, some first and second degree burns of the skin or exposure to chemicals can also cause blisters. These blisters all have a common pathology regardless of the traumatic causation.
When the epidermal layer of the skin is traumatized, an acute accumulation of clear extracellular fluid develops very rapidly between the epidermal and dermal layers of the skin. Secondary inflammation then occurs as part of the healing process. If the epidermal layer opens, the secondary inflammation also may be associated with infection and, as a result, may develop purulent fluid with an infiltration of white blood cells. Moreover, the actual exposure of the dermal layer of skin often results in pain. The present invention takes advantage of the finding that all of these symptoms can be alleviated in whole or in part by significantly reducing the fluid in the acute stage of the blister while maintaining the integrity of the epidermis.
Immediately following a burn to the skin which results in a first or second degree burn, there is an acute inflammatory reaction in the burned skin consisting of acute dilation of blood vessels with leakage of fluid into the extravascular and extracellular space in the burned skin. In addition, in second degree burns there is characteristically a blister filled with clear fluid on the skin surface. Further, there is a great deal of pain in the injured area which may last up to seven days or more.
In view of the deficiencies in prior treatment, it is an important object of the present invention to provide a treatment for blisters that is safe and can be used by the patient for effectively relieving adverse symptoms or improving the blistered skin and in reducing or eliminating the associated pain.
Another object is to provide an adhesive patch for treating blisters.
These and other more detailed and specific objects of the present invention will be better understood by reference to the following figures and detailed description which illustrate by way of example of but a few of the various forms of the invention within the scope of the appended claims.
This invention provides a moist and flexible hydrogel, most preferably in the form of a flexible but dimensionably stable patch for covering the blister by which the fluid volume within the skin blister is significantly reduced. This reduction results from placing a hypertonic hydrogel layer in direct contact with the blister so as to produce an osmotic imbalance between the liquid within the blister and the hydrogel. After the patch has been applied, the fluid is drawn out of the blister by osmotic force through the raised epidermis which, upon being hydrated externally by the gel, can then act as a semi-permeable membrane. The structural integrity of the epidermis remains intact due to the protection provided by the patch. Following this, the epidermis will lay down on the dermis. It was found that the epidermis will then heal to the dermis without pain like a split thickness skin graft. Thus, the present invention provides a means of reducing accumulated extracellular fluid contained in the blister. The osmotic imbalance persists while the patch is in place and continues to draw fluid from the low concentration in the blistered skin to the high concentration in the hypertonic hydrogel. This invention therefore concerns a method for treating blistered skin by applying directly to the blistered area a moist, flexible, hypertonic hydrophilic gel patch. While not essential, the gel preferably has a tacky, i.e., pressure-sensitive adhesive, surface enabling the patch to be self-bonding to the skin. This bond enhances hydration of the skin and the transfer of fluids. The patch also includes a backing such as paper, cloth or plastic that acts as a support for the patch and a water-based hypertonic hydrogel layer applied to the backing. The tacky pressure-sensitive adhesive surface of the gel layer, when present, bonds the hydrogel and the patch itself to the skin. The hydrogel layer forms a water bridge between itself and the outer surface of the skin that makes up the top of the blister. This hydro bridge allows the flow of fluid from within the blister, which has a lower osmotic pressure than the osmotic pressure in the hydrogel layer.
The hydrogel layer comprises water and, as a thickening or gel forming agent, a hydrophilic natural or synthetic polymer dispersed in the water. The polymer can comprise a high molecular weight hydrophilic carbohydrate such as karaya, cornstarch, or kelp gel and/or a synthetic hydrophilic polymer such as polyacrylamide, a polyionic gel, or polyacrylic acid. A humectant such as an alcohol containing two or more hydroxyl groups, i.e., a polyhydric alcohol, is preferably employed to keep the adhesive layer moist. Any water soluble solute such as salt or an alcohol is dissolved in the water in a quantity sufficient to raise the osmotic pressure above that within the blister; namely, to a value over about 308 mOsmol/L so as to maintain the adhesive hydrogel layer in a hypertonic state with respect to the interior of the blister. As already noted, the adhesive hydrates the outermost layer of skin above the blister. Consequently, the hydrogel adhesive, when applied to a patient, forms a hydrophilic bridge with the patient""s normally dry outer skin layer, the stratum corneum, which allows fluid transport between the skin and the patch across the hydrophilic bridge. With the patch in place on the skin, the fluid in the blister is then transported to the hydrogel layer by osmotic pressure to thereby improve or entirely relieve the blistered condition. After the fluid is gone, the epidermis will then heal to the dermis, much like a split thickness skin graft and without pain. It was also found that the invention provides substantial and sometimes complete removal of pain as soon as it is applied, probably because of its cooling effect since the patch acts somewhat like a heat sink in very good thermal contact with the skin with moisture evaporating from its upper surface.
Another aspect of the invention is the hypertonic moisture-containing adhesive patch itself. The patch as noted above contains a flexible backing and a lower hydrophilic, pressure-sensitive adhesive layer containing water, a hydrophilic polymer dispersed in the water, and a dissolved substance. The relative amounts of the solute and solvent are adjusted such that the osmotic pressure of the patch is above that of the underlying tissue of the patient so as to maintain the adhesive hydrogel layer in a hypertonic state with respect to the fluid in the blister. The tacky surface of the adhesive layer wets the normally dry skin surface and creates the hydrophilic bridge with the patient""s elevated skin layer. This allows the free transport of fluid from the blister.